Both the location and the date are notable for the Michigan bird. It is very hard to find Black Scoter inland in Michigan and it is rare to find it in the spring in the Great Lakes area. That being said, the hundreds/thousands of Greater Scaup that gather on the west side of Point Pelee, Ontario in April and early May, attract good numbers of Surf Scoters and also a few Black Scoters such as the one shown below. As for the male Black Scoter at Port Sanilac, I think I have seen less than 5 adult males in the lower peninsula of Michigan in almost 60 years of birding. In contrast, females/immature males are an annual sight though uncommon in southern Michigan in the fall.